The present invention relates to holding arrangements for tools or workpieces in general, and more particularly to a tool and workpiece holding arrangement for material-removing machining, which includes a primary holder and a replaceable secondary holder which have respective profiled engagement surfaces by means of which they are form-lockingly connectable with one another with the aid of corresponding clamping mechanisms.
In view of the fact that modern machine tools are designed for the performance of material-removing machining operations which are very different in character, such as drilling, milling and turning, numerous requirements are also placed on the holding arrangements for the various tools, or for the workpieces, as a result of these varied machining tasks, on the one hand, and in view of an automatic performance of the operations with corresponding tool or workpiece exchange, on the other hand.
Besides high flexibility for the accommodation to the respective machining tasks and requirements as well as to the various machine configurations and concepts embodied therein a high stability both in the static sense and in the dynamic sense must be achieved, even when considering the various material-removing operations with fundamentally different loadings. There must be provided a high exchange and repetition accuracy, in order to be able to satisfy narrow manufacturing tolerances, even during automated performance of the various operations. There must further be provided a simple handling capability both for the manual and for the automatic exchange and, despite the complexity of the requirements, the holding arrangement must be capable of being produced in an economical and relatively inexpensive manner.
The heretofore known holding arrangements for the material-removing machining can satisfy only some of these requirements, owing to their respective configurations and structural features. Such holding arrangements are normally designed by the manufacturer for only one predetermined material-removing operation, for example, for a turning operation or for a drilling operation, and for the loadings which result from such predetermined operations. These do not, however, include any profiled surfaces between the primary holder and a replaceable secondary holder, but are rather provided in each instance with one or two mutually engaging projections corresponding to the respective loading case; these are known from the European Patent Application EP-A-001-0074, German published Patent Application DE-A No. 30 07 440 and the German Patent DE-PS No. 31 08 439; additionally, there is already known, from the German Patent Application DE-A No. 32 28 521 a holding arrangement in which the mutually facing surfaces of the replaceable secondary holder and of the primary holder are profiled and positively engage one another after the corresponding actuation of the clamping mechanisms. The profiled portions utilized in this construction are constituted by cooperating teeth, which are configured in the manner of a so-called Hirth tooth arrangement, and where the tooth arrangements are arranged radially with respect to a center that is situated in the middle of the respective engagement surfaces. Owing to this configuration, it is already possible to transmit fundamentally different forces, such as those resulting from the different material-removing measures, especially axial bending forces, radial bending forces, but also turning moments or torques, at the connecting region of the replaceable secondary holder and the primary holder. Moreover, a self-centering effect takes place after the activation of the clamping mechanism, so that there is attained a high accuracy when replacing or exchanging such holders. Due to the self-centering effect, the clamping mechanism itself can be provided with relatively wide tolerances in the region of the cooperating elements, so that the relatively coarse initial approach accuracy, which is obtained during the automatic holder exchange by the automatic gripper equipment is, nevertheless, sufficient. On the other hand, the adaptability of the holding arrangement of this construction to the respective machining requirements and machine concepts is nevertheless relatively low and, in particular, the manufacturing costs of such tooth-engagement arrangements are relatively high, resulting from the requirement for producing the teeth one-by-one, and always in a slightly different orientation with respect to the center. Extremely narrow limits are imposed on the construction of the enlargement and any supplements of the engagement surfaces beyond, so to say, the basic scheme of the engagement surface, which is often needed for certain types of manufacturing operations. Such supplemental- or enlargement-surfaces are often desired for the performance of certain manufacturing operations. They are to be arranged at predetermined locations for the secure support of the tool or of the workpiece, and are to be provided with respective tooth-engagement arrangements or toothed-engagement sections. However, an economical producibility of the latter can only be realized, when these further toothed-engagement sections are arranged in alignment with the tooth-engagements of the basic engagement surface so that, in this construction, as a result of the central orientation of the toothed arrangements of the basic engagement surface, there are hardly obtained any meaningful arrangements and/or configurations and, basically, any enlargement or supplements suitable for adaptation to the various material-removing operations are absent from this particular construction.